Noxious weed look alikes – don’t pull the wrong plant!

noxious weeds Scentless chamomile thistle

Noxious weed look alikes – don’t pull the wrong plant!

Admin    July 12, 2019   

by Irene Shonle

It is heartening to see so many people being committed stewards of their land who are working to eradicate the noxious weeds on their property.  Thank you to everyone who is participating!  A word of caution -  it is possible to be a little too enthusiastic. This happens when someone pulls or treats the wrong plant – a plant that has the misfortune of looking like a noxious weed. These look-alike plants are often native, and can provide good habitat for pollinators, or at the very least, will occupy space that otherwise could be invaded by a noxious weed, so it’s best to learn how to distinguish which is which.

Some of the most common mistaken identities up here are:

• Golden banner/yellow toadflax,
• Pineapple weed/scentless chamomile,
• Cutleaf daisy/oxeye daisy 
• Fireweed/purple loosestrife.

Golden banner is a native plant – it blooms in the spring, and has solid yellow flowers, and three-lobed (trifoliate) leaves. Yellow toadflax blooms in the second half of summer with two-tone yellow flowers with a darker throat, and has strap-shaped leaves.

Golden banner

Yellow toadflax

Pineapple weed, while an introduced plant, is not on the noxious weed list. It is, however, having a very good year, and can be easily controlled by hoeing or pulling.  It has ferny leaves that, when crushed, smell like pineapple. The whole plant only gets to 6-8” tall at the most. It develops small yellow buttons, but never white ‘petals’ (ray flowers). Scentless chamomile also has ferny leaves, but they have no odor (the plant names give good ID clues). It gets up to 3’ tall, and has hundreds of white flowers.

Pineapple weed

Scentless chamomile

Cutleaf daisy is a native plant with small white flowers and finely cut leaves that could look a little ferny. It can (and has been) mistaken for pineapple weed, scentless chamomile and oxeye daisy. The flowers on the native bloom in the spring, and the foliage has no smell. The whole plant is no taller than about 4” tall. Oxeye daisy blooms mid-summer, and has much larger flowers, as well as broader leaves with teeth (not ferny). The plant grows 1’-3’ tall.

Cut-leaf daisy and penstemon

Oxeye daisy

Fireweed is a native plant with 4 pink petals. It blooms mid-summer to fall. The leaves are alternate, and the plant can grow up to 4’ tall. Purple loosestrife is not known to be up at this elevation, but people have frequently pulled out fireweed by mistake. Loosestrife has opposite leaves (or even whorled – meaning that four leaves come out of the stalk at the same place). It has 5-7 purple petals and can grow up to 8’ tall. 

Fireweed

Loosestrife

Finally, we have many wonderful native thistles, and it’s easier to just learn to recognize our two common noxious thistles, Canada thistle and musk thistle, rather than all of the native thistles. Musk thistle has large, solitary purple flowers with a formidable row of teeth under the flower. The leaves have a whitish edge. Canada thistle usually forms thickets due to the root system, and has clusters of small purple flowers.  See below table for a quick reference to distinguishing these plants.

Native plant	Bloom	Leaves	Noxious weed	Bloom	Leaves
Golden Banner	Solid yellow, spring	Three-parted	Yellow toadflax	Two-toned with a darker throat, Mid-late summer	Strap-shaped
(Pineapple weed – not native, but not noxious)	Just a yellow button, spring-mid summer	Ferny, smells of pineapple	Scentless chamomile	White flowers, Mid-late summer	Ferny, odorless
Cutleaf daisy	Small white flower, spring	Finely cut, a little ferny	Oxeye daisy	Large, white, blooms	Small teeth on leaves
Fireweed	4-petals, pink, mid-late summer	Alternate leaves	Purple loosestrife	5-7 pink petals, mid-late summer	Square stem, 4 or more leaves come out of same place on stalk (whorled)
Native thistles	Varies – white, pink, brownish	Varies – usually very white on underside	Noxious thistles (especially Canada and Musk)	Purple-pink	Varies

For more information and pictures, we have a brochure online: https://gilpin.extension.colostate.edu/wp-content/uploads/sites/29/2016/09/Noxious-weed-look-alikes.pdf.

For more information on thistles, see this brochure: https://www.larimer.org/sites/default/files/uploads/2017/finaltg2nded.pdf

Or here: https://gilpin.extension.colostate.edu/programs/natu/native-thistle/

Irene Shonle is the CSU Extension Agent and Director in Gilpin County

Weeds, NOT landscape plants, by Todd Hagenbuch

noxious weeds

Weeds, NOT landscape plants, by Todd Hagenbuch

Admin    July 21, 2017   

This time of the year, flower gardens throughout the area are in full bloom with all kinds of beautiful foliage.  Some of those flowers are annuals, some perennials.  Some are from seed, others grown from bedding plants, and others gifts from friends or neighbors.  Some are natives, some are introduced, and more importantly, some are actually noxious weeds.

A noxious weed is any weed that has been determined by the State of Colorado to negatively impact or threaten our native or agricultural ecosystems.  Typically a plant that was introduced from Europe, Asia, or Africa, these weeds have abilities to out-compete our native plants, meaning they spread unchecked throughout our landscape.  Unfortunately, many of these plants are still being planted in yards and gardens throughout our area, and are sold by nurseries or seed companies and purchased by unsuspecting homeowners who are looking for spreading, low maintenance plants with attractive flowers.  While that’s exactly what they get, homeowners also get themselves and their neighbors into a mess, not to mention that they are breaking the law by planting these noxious weeds.­

List A noxious weeds need to be eradicated, by law, whenever they are found on any property in order to protect communities and the state as a whole. There are several plants that I see in landscapes that are List A species.  

In our area, Orange hawkweed (Hieracium aurantiacum) is one of the biggest List A offenders. It is believed that this plant was sold and planted by a local Steamboat Springs landscaper for several years in the recent past. The orange flowers are beautiful, but this plant spreads quickly and can invade roadsides, lawns, common areas, and more.

Myrtle spurge (Euphorbia myrsinites) is another common plant in home landscapes that needs to be eradicated.  The leafy plant has yellow-green blooms, which are really small flowers surrounded by petal like bracts.  I see this plant in a yard near my sister-in-law’s house when I visit her and it gives me heartburn whenever I see it.

Purple Loosestrife (Lythrum salicaria) is a perennial plant that is found in our area, especially in wet areas. While it looks a lot like our native fireweed, this bad actor can create millions of seeds per plant and those seeds remain viable for 2-5 years. If you find this one in your yard, you’d better get rid of it quickly!

List B noxious weeds are weeds that need to be controlled to limit spread.  You should control these in a yard situation, too, as they can escape to other areas quickly and cause havoc.

Dame’s Rocket (Hesperis matronalis) is a 4 foot tall plant of purple or lavender colored, 4-petaled flowers. It has been included in many wildflower seed mixes, and tends to escape into pastures, forests, and more.

Scentless chamomile

Oxeye Daisy (Chrysanthemum leucanthemum), not to be confused with the larger Shasta Daisy, is another flower that is sometimes included inappropriately in wildflower mixes and is prevalent in our area, both in landscapes and in pastures.  

Other List B species to be aware of include Common tansy (Tanacetum vulgare) and Scentless chamomile (Matricaria perforata).  Attractive plants on Colorado’s Watch List (plants that are a potential threat to our environment) include Baby’s breath (Gypsophila paniculata), and Yellow flag iris (Iris pseudacorus).  Follow this link for a detailed list with photos: https://www.colorado.gov/pacific/agconservation/noxious-weed-species.

Knowing what you’re planting in your yard is the first step in helping to halt the spread of noxious weeds. Always check wildflower seed packets before planting and check with your local Extension office to see if something you’re considering planting is actually a noxious weed, or if you need help identifying suspicious plants.  Your neighbors will thank you and you can continue to be a law-abiding citizen.

Todd Hagenbuch is the Agriculture Extension Agent for CSU Routt County Extension.

Weed Wranglers … Unite! by Jan Boone

noxious weeds

Weed Wranglers … Unite! by Jan Boone

Admin    March 30, 2017   

Musk thistle

Consider the warm dry winter that’s just ended and how with a bit of Spring moisture, weeds will soon make their annual appearance in your garden and surrounding landscape.  Whether you’re a local veteran of yearly weed battles; a new resident from out-of-state or someone who’s just ‘moved up the hill’ from the more urban surroundings of the Metro area, facing weeds in the foothills can be daunting!   As if gardening at altitude isn’t challenging enough, the dandelions and diffuse grassy clumps of lower elevations are for the rookies.  You’ve just entered the big leagues of weed wrangling!  Consequently, this is a good time to dust off your garden tools and read up while we highlight steps on wrangling popular local offenders.  Let’s review the basics from weed identification to eradication and control.   Additionally, as foothills residents, we shouldn’t forget that there are many state agencies that can help with the identification of the weed you’re looking at. (See resources listed below). After all, you can’t effectively eradicate or control something you know nothing about, right?? 

First, you must learn to recognize the weed you are trying to wrangle. Is it a native plant growing here before you arrived, that simply grows where you don’t want it to grow, or a non-native invasive plant with a potentially harmful impact if allowed continued growth?  Consult Colorado’s Department of Agriculture lists of Noxious Weeds (https://www.colorado.gov/pacific/agconservation/noxious-weed-species) that can help pinpoint and inform you of things you need to know about eradication, management and research mandated from state to local levels.  Also, in the near future, the Evergreen Farmer’s Market, staffed by Jefferson County Master Gardeners, will have their annual Weed Clinic Day on July 11^th this year.  It is a one day partnership with the Evergreen Audubon Group where you can bring your own weeds, see their samples and learn about what you need to do for eradication. Be proactive in refreshing your knowledge on how and when certain weeds may develop.  Is it a winter or summer weed? Think about how seeds will spread; the growth habits that may include spreading along the ground with runners or climbing up stationary landscape elements, including other plants.   These are all some of the varying traits of a weed’s growth pattern and life cycle.

Secondly, wrangling or controlling is more beneficial when you know specific traits and can develop your best management practices.  While our weeds may seem too haunt you year-round, perhaps yours is simply an annual, perennial or biennial weed not being controlled effectively.  Knowing this alone will assist you with more effective control methods.  That guaranteed home recipe from your neighbor for vinegar based weed killer is not a winning formula.  Are you in need of some gentle, quiet time?  Grab a container and go outside with your favorite weeding tool and simply work on manual eradication.  Weed whackers may do the job quickly on grasses but can also help to spread seeds and destroy wildflowers if you do it at the wrong time! A critical note to include here is to choose wisely and do your research if you go the route of chemical or biological control. 

Cheat grass taking over

Lastly, for long term management, be patient, have a plan, research and talk to knowledgeable, experienced people who know effective control methods.  Don’t just reach for the long-term bottle of weed control on your next trip through the store. We live in a beautiful environment and many animals and beneficial insects rely on flowers for pollen, food sources and other elements to sustain their lives. Managing and controlling weeds on your property with a thoughtful plan contributes to the enjoyment of your garden and landscape.  It’s crucial for all of us, especially when considering wildfire mitigation.  I wish happy wrangling to all.  May your efforts be rewarded with bountiful outdoor pleasure this Spring, Summer & Fall.

Here’s my supplemental reference list of easily recognizable offenders, plus 5 general resources for more information.

Noxious weeds:

Bindweed- Perennial w/extensive root systems. Grows in dense, low mats.  Sometimes called Wild

Morning glory. Seeds can be viable for half century!

Cheat Grass- Several varieties are among the Brome/Grass family. Seed pods germinate in Fall, drop and

overwinter. Already we are seeing new shoots come up.

Common Burdock – biennial, grows to 10’ tall. Burs stick to animals and clothing.

Knapweed- Several varieties are found, all from Sunflower family.  They include Diffuse, Spotted and

Russian.

Mullein (Common)- Found in many open fields. Tall flowering stalks with yellow flowers.

Myrtle Spurge- low growing perennial in clumps. Easily spread in shade among rocks. Sap can be

irritating to skin.  Several varieties are found, all invasive.

                                Oxeye Daisy –creeping perennial with attractive white flowers.

Thistle- Three are biennial ( Bull, Musk and Scotch), and one (Canada) is a creeping perernnial that is hard to eradicate.  

Yellow Toadflax- Perennial often mistaken as a wildflower. Reproduces by seed and underground

rhizomes.  Close cousin is Dalmatian Toadflax, both highly invasive.

Nuisance weeds:

Broadleaf plantain- A fibrous rooted perennial.  Seed stalks a favorite of birds and small

animals. 

Shepherd’s Purse-Mustard family member.  Early Spring bloomer.  Generous seed production.

Sagewort- Perennial native of Europe, from Aster family.  Favorite of rabbits and some birds.

Mallow- Includes Common and Velvet Leaf varieties. Originates from Europe and Asia.

Dandelions- Crucial in supporting bees due to early Spring blossoms and pollen. Treat them as

wildflowers and enjoy the color!!

Pennycress (Field) – Annual w/large taproot. Oils researched as potential bio-fuel in mid-west. Attracts

small bees and flies.

 Resources with good colored pictures for identification:

www.ext.colostate.edu for Noxious Weed Management and Pocket Guide. 2013.  Good, basic management guide and further website listings.

www.colorado.gov/pacific/agconservation/noxious-weed-species for Noxious Weed species (A,B,C Lists).

http://jeffco.us/weed-and-pest/weeds/noxious-weed-information/for Noxious Weed Identification and Control . Very user friendly listing by name or flower color.

Weeds of the West, Tom Whitson, editor, 2009 Revised edition, Western Society of Weed Science.

Can be cumbersome with a scientific weed family key for use, but easily referenced common name index and glossary. Beware that many plants are native plants (that can be problematic in pasture/rangeland situations).

Garden Smart Colorado – A Guide to Non-invasive plants for your garden, Colorado Weed Management Association, 2012.  Great resource for basic alternative ornamental plantings, including invasive plant notations.